Folding mechanism of foldable table in the market, such as ZL02259585.6 issued in Aug. 6, 2003 in CNPAT comprises a table top, a leg portion and a supporting portion, the upper portion of legs formed rotatable connection with the table top, the supporting portion comprises a first pivotally connecting with the leg portion, a second pivotal-connection portion for pivotally connecting with the table top and a ring, the first pivotal-connection portion pivotally connected with the second pivotal-connection portion, the table top, the leg portion, the first pivotal-connection portion and the second pivotal-connection portion formed a four-rod folding mechanism, after being unfolded, the folding mechanism is fixed in a unfolded position by the ring which limit the rotation between the first pivotal-connection portion and the second pivotal-connection portion. However, the first pivotal-connection portion and the second pivotal-connection portion of the supporting portion of the folding mechanism can rotate relative to each other, thus the mechanism has a complicated structure, many rods, high cost, unstable when forced and unstable structure; locked by the ring after being unfolded make the locking unstable, accordingly, the table is unstable.